The present invention relates to sootblowers for rotary regenerative air preheaters and particularly to a swing-arm sootblower which is driven at a constant speed or angular velocity across the air preheater rotor.
Soot or other related materials from flue gases tend to deposit over a period of time on the heat transfer surface of the rotor of a rotary regenerative air preheater. As these deposits build up, the flow paths for the air and flue gas become blocked and the heat transfer capacity is reduced. Therefore, it is common for these air preheaters to include devices for blowing air or steam at high velocities into the rotor to dislodge the deposits.
The typical sootblower for a rotary regenerative air preheater employs a swing-arm mounted for rotation through a set angle or arc with one or more nozzles at the end which blow the sootblowing medium (air or steam) onto the rotor as the rotor turns and as the swing-arm rotates through the arc. The sootblower is normally mounted on the cold end of the rotor which is the outlet end for the flue gas.
The prior art sootblowers have employed a drive mechanism which includes a worm gear and a worm wheel which rotates a lever throw arm. A connecting link attaches the lever throw arm to a lever attached to the sootblower arm mounting plate. This linkage arrangement causes the lever and the sootblower mounting plate to reciprocate back and forth through an arc. This also results in the swing-arm sootblower to constantly change speed or angular velocity as it sweeps across the rotor. At the beginning and end of its sweep, the velocity is zero with the maximum velocity being at the center of the sweep. Between the center of the sweep and the beginning and end, the velocity is constantly speeding up or slowing down due to the linkage arrangement. Therefore, the energy of the sootblowing medium is concentrated towards the two ends of the nozzle travel. This causes a more rapid deterioration of the heat exchange elements in the rotor usually toward the center and outside periphery of the rotor. This type of prior art sootblower is schematically illustrated in the drawings and will be further explained hereinafter.